A conventional tool box is generally includes a box-like body and a cover which is pivotally connected to the box. The box-like body and the cover are manufactured by way of blowing which employs blowing machine to blow air into plastic material in a mold so as to form the hollowed board. The blowing process is properly suitable for manufacturing tool boxes having simple structure as described above. However, tool boxes nowadays are required to include multiple layers so as to receive more tools or bits. The multiple-layer tool box needs more molds and the molds have complicated figures, this usually costs a lot.
The present invention intends to provide a tool box which is assembled by two foldable parts and each part includes two or three boards. The boards are connected with each other by engaging projections in one board with recesses in another board.